The present invention relates to a homokinetic joint comprising an element having the shape of a tripod connected to one of two shafts to be coupled and a tulip element connected to the other of said shafts, the tripod element having three trunnions on which are rotatively mounted rollers received in three rolling ways provided in the tulip element, and axial retaining means for maintaining an axial connection of the two parts of the joint.
French patent application FR-A-2,398,924 describes and shows a homokinetic joint of this type in which the rolling ways comprise tracks having a circular cross section and the axes X--X of which are parallel to the axis of the shaft connected to the tulip element, and the axial retaining means comprise an intermediate element defining a convex spherical outer surface received in a concave spherical cavity provided in axial branches of the tulip element.
In the embodiment shown in FIGS. 7 and 8 of this document, the intermediate element has three slots or notches in which the three trunnions of the tripod element are received and a first planar surface perpendicular to the axis of the tripod element. A first contact zone confront the tripod element to enable the latter to move in a plane perpendicular to its axis. And, a device is provided for axially retaining the tripod element in the intermediate element.
In order to enable the tripod element to move in a direction perpendicular to its axis, the three slots in which the three trunnions of the tripod element are received are so dimensioned as to provide the clearances required for the necessary relative movement between these two elements to permit flexing the two parts of the joint at an angle. This very important dimensioning of the slots contributes to a reduction in potential size of the convex spherical outer bearing surface of the intermediate element in the concave equatorial spherical recess provided in the axial branches of the tulip element and consequently a reduction in the potential maximum flexing angle of the homokinetic joint.
The overdimensioned slots relative to the outside diameter of the trunnions, in practice require arranging the axial retaining device of the tripod element in the inner end of the intermediate element, i.e. at the end remote from the end through which the tripod element is introduced. This structure on the one hand has a drawback in that the assembly of the homokinetic joint is rendered very complex, since access to the mechanical connecting means constituting the axial retaining device is very difficult during the assembling operation, and on the other hand in that it requires axially offsetting the plane of the zones of contact between the tripod element and the intermediate element relative to the equatorial plane of the latter. Furthermore, the retaining device proposed in this document requires the provision of an aperture at the inner end of the intermediate element which weakens the structure and again reduces the convex spherical outer bearing surface thereof.
It was also proposed in FIGS. 9 to 11 of this document to construct the intermediate element in three segments each having a spherical wall constituting a ball joint and two end walls defining parallel planar surfaces adapted to cooperate with lateral contact zones confronting the tripod element. While this solution overcomes some of the aforementioned drawbacks, it is very complex with respect to both the realization of the segments and their assembling and mounting.